Recently, in a vehicle, a number of safety devices has been provided in order to ensure safety of an occupant in case of a traffic accident. In a number of safety devices, an air bag device is a typical safety device.
In the air bag device, an impact generated on the vehicle by a collision is detected by a G-sensor. Based on a signal from the G-sensor, an operating signal for operating the air bag device is inputted to the air bag device which is provided in the center of a steering wheel for a driver or a dashboard panel of a passenger seat. When the operating signal is inputted to the air bag device, an inflator accommodated in the air bag device is ignited. By this ignition, gas for inflating an air bag is expanded. Then the air bag is quickly inflated by the gas, and the occupant sitting on a front seat (for example, the driver seat or the passenger seat) is protected.
For example, in the foregoing air bag device, when a child sits on the seat or a child restraint system (child seat) is mounted to the seat with an infant sitting on, an inflating amount of the air bag needs to be somewhat reduced as compared to the inflating amount of the air bag as an adult sits on the seat.
As a typical occupant weight detecting device for detecting the occupant sitting on the seat, a weight measuring device, which includes a strain gauge provided on the seat for measuring weight of the seat, is known. For example, a known weight measuring device is disclosed in a Japanese Patent Laid-Open Publication No. 11 (1999)-337393. In the weight measuring device disclosed in the foregoing publication, four load detecting sensors are provided on front and rear sides at the bottom of a seat. Each pair of unselective front and rear load detecting sensors is electrically connected to a circuit, and an output from each pair of unselective front and rear load detecting sensors is detected by the circuit. The weight measuring device calculates the weight of the seat based on the output from the circuit.
However, the foregoing load detecting sensors are provided on the seat in the vehicle deferent from a static position, error may be generated on the load detecting sensors due to vibration at running or variation of environment in a vehicle compartment. Thus, when the occupant sitting on the seat is detected by using the defective load detecting sensor, load applied to the seat can not be correctly detected, and the error generated on the load detecting sensor has to be detected.
The present invention therefore seeks to provide an occupant weight detecting device capable of detecting error generated on a load detecting means when load applied to a seat is detected.